It is thought that neutrophilic leukocytes show a germicidal activity to foreign invaders in living bodies by a wondering reaction, a feeding action, generation of superoxide radical (O.sub.2.sup.-) and release of lysosomal enzyme and play an important role in protection of living body. While neutrophilic leukocytes have the above reaction for living body protection, it has been made clear that the superoxide radical released by tissues or neutrophilic leukocytes during ischemia of tissues and subsequent blood re-perfusion or during acute inflammation at early stage destroys cells, causing functional disturbances of tissues [B. R. Lucchesi: Annual Review of Pharmacology and Toxicology, Vol. 26, p. 201 (1986); B. A. Freeman et al.: Laboratory Investigation, Vol. 47, p. 412 (1982); E. Braunwald, R. A. Kloner: Journal of Clinical Investigation, Vol. 76, p. 1713 (1985); J. L. Romson et al.: Circulation, Vol. 67, p. 1016 (1983)].